Re: [Paddlewise] GPS observation

From: Dan Hagen <dan_at_hagen.net>
Date: Tue, 5 Sep 2000 09:15:13 -0700
Hi Colin. I think that your problem with the use of the Garmin compass
screen stems from a misunderstanding regarding the way it works (which
may in turn be due to Garmin's poor documentation). If I understand
what you are saying below, you seem to think that the compass pointer
is supposed to point to the waypoint. It does not, and is not designed
to do so. I could see why one might be confused, since the summary of
this feature in the Garmin manuals describes the pointer as "pointer
to waypoint". This is very misleading. If you dig a bit deeper into
the function of the pointer (by reading the documentation for the
fully featured Garmin receivers, not the "dumbed-down" eTrex) you will
find that the pointer does NOT point to the waypoint, but rather is
provides information that is much more useful than this. So what is
the function of the pointer, if not to point to the waypoint?

The pointer on the compass page is a course-correction pointer--it
shows the discrepancy between your heading (actual direction of
travel, or "track" angle to use Garmin's nomenclature), and the
bearing to the waypoint.  For example, if you are holding a 30-degree
ferry angle and this is the correct ferry angle to take you to your
waypoint, the pointer will point straight ahead. This shows that you
are holding the correct ferry angle, and should keep paddling in the
same direction. (Do not correct your angle.) On the other hand, if
your ferry angle is not correct (so that you are not heading directly
towards your waypoint) the pointer will point left or right
(indicating the direction and angle to correct your course so as to
track directly to the waypoint). This becomes obvious if you are using
a more fully-featured GPS (such as a Garmin 12), since on the compass
page it will tell you simultaneously both your track angle and the
bearing to the waypoint. The arrow is simply a graphical
representation of the difference between these angles.

I hope that this clears things up. I certainly agree with you that one
should carry a deck compass in addition to the GPS, but not for the
reason that you state.

Happy paddling!

Dan Hagen



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Received on Tue Sep 05 2000 - 09:31:19 PDT

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